ASTRO: NGC 7694-5

NGC 7694 is an irregular Magellanic galaxy in Pisces. NED and the NGC
Project both class it as Im Pec? The MCG catalog has a couple comments
I can't understand. It reads: "It is similar to M 82..." Then adds:
"...merged with a star brighter than itself." How an irregular dwarf
galaxy can be compared to M82 baffles me. It does have a bright off
center region that I suspect is the "star". I don't see it as anything
but the brightest part of the galaxy. No other catalog makes reference
to a star there that I could find except for the HST Guide Star Catalog
which lists lots of things as stars that aren't. It does the same for
NGC 7695, the companion to NGC 7694. So it is worthless for this
purpose. The HST hasn't imaged the area so that can't help either.

I included this one on my list for its irregular shape and lots of HII
regions that show as blue blobs in my image. It is also a strong IR
emitter being in both the IRAS and 2MASS catalogs so there is a lot of
star formation going on that is hidden by thick dust. Its the dust
warmed by these new stars that likely accounts for the IR radiation.

It's companion is NGC 7695 which is classed as cE2? Pec? by NED and S0
by the NGC project. Quite a disagreement. The cE in cE2 means it is a
compact elliptical galaxy and the 2 means it is somewhat elongated.
It's core is elongated about as I'd expect for an E2 galaxy but it has
an extensive even more elongated halo. This is what likely caused the
S0 class by the NGC project and the Pec? label by NED. I won't try to
guess who is right. Since they use different classification systems
both may be "right."

More important is whether these two are interacting. The massive star
formation of NGC 7694 could be due to other factors but it is often
caused by interaction so it's quite likely they are interacting as they
have very similar redshifts. A compact galaxy holds its stars quite
tightly which results in little distortion unless it is involved in a
direct hit with another galaxy. Just passing by wouldn't cause a lot of
distortion but could cause the larger halo we see around NGC 7695. An
irregular galaxy has a loose hold on its contents so can be greatly
affected by a close encounter.

I've included a link to the Sloan image of this pair. It seems to show
the core of NGC 7694 as much bluer than I do. It records near
ultraviolet light that gets through our atmosphere which I don't. That
is likely the cause of the color difference. While it also records IR
light most of the IR a galaxy emits due to dust warmed by star formation
is at wavelengths greater than Sloan can see.

While Sloan has imaged the area the data is yet to make it into NED so I
wasn't going to make an annotated image. But then I saw there were 4
other asteroids in the frame besides the obvious one. They were too
faint to point out without annotation and a few galaxies were in NED
with redshift information so I decided to make one anyway. In doing so
I found one galaxy, WIG R00J233224443-02450563, with a redshift of
z=1.110560 which puts it at over 8 billion light-years. That is the
WiggleZ Dark Energy Survey. It tends to list very high redshift
galaxies. Makes me wonder if these are quasars rather than galaxies
that I am seeing. Or is it just a very bright but normal (for one that
far back in time) galaxy I'm picking up. It is in the right side of my
image and labeled with its magnitude as well as distance using NED's 5
year WMAP calculation. For more on the WiggleZ survey see:
http://wigglez.swin.edu.au/site/ The page says it covers galaxies with
a redshift of 0.2 to 1 yet this one exceeds 1 though not by a lot. For
more on the survey including where the name comes from see:
http://www.science.org.au/nova/115/115key.html

It seems most asteroids I catch in my images are moving in retrograde
motion. These are the exception as all are moving in prograde that is
to the east (left).

Sloan image:
http://cseligman.com/text/atlas/ngc7694wide.jpg

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

The link to the Sloan image has gone bad. Fortunately, I'd saved a copy which I'm attaching.

Rick

Rick,

this looks like a miniature version of NGC 4490.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...

NGC 7694 is an irregular Magellanic galaxy in Pisces. NED and the NGC
Project both class it as Im Pec? The MCG catalog has a couple comments
I can't understand. It reads: "It is similar to M 82..." Then adds:
"...merged with a star brighter than itself." How an irregular dwarf
galaxy can be compared to M82 baffles me. It does have a bright off
center region that I suspect is the "star". I don't see it as anything
but the brightest part of the galaxy. No other catalog makes reference
to a star there that I could find except for the HST Guide Star Catalog
which lists lots of things as stars that aren't. It does the same for
NGC 7695, the companion to NGC 7694. So it is worthless for this
purpose. The HST hasn't imaged the area so that can't help either.

I included this one on my list for its irregular shape and lots of HII
regions that show as blue blobs in my image. It is also a strong IR
emitter being in both the IRAS and 2MASS catalogs so there is a lot of
star formation going on that is hidden by thick dust. Its the dust
warmed by these new stars that likely accounts for the IR radiation.

It's companion is NGC 7695 which is classed as cE2? Pec? by NED and S0
by the NGC project. Quite a disagreement. The cE in cE2 means it is a
compact elliptical galaxy and the 2 means it is somewhat elongated.
It's core is elongated about as I'd expect for an E2 galaxy but it has
an extensive even more elongated halo. This is what likely caused the
S0 class by the NGC project and the Pec? label by NED. I won't try to
guess who is right. Since they use different classification systems
both may be "right."

More important is whether these two are interacting. The massive star
formation of NGC 7694 could be due to other factors but it is often
caused by interaction so it's quite likely they are interacting as they
have very similar redshifts. A compact galaxy holds its stars quite
tightly which results in little distortion unless it is involved in a
direct hit with another galaxy. Just passing by wouldn't cause a lot of
distortion but could cause the larger halo we see around NGC 7695. An
irregular galaxy has a loose hold on its contents so can be greatly
affected by a close encounter.

I've included a link to the Sloan image of this pair. It seems to show
the core of NGC 7694 as much bluer than I do. It records near
ultraviolet light that gets through our atmosphere which I don't. That
is likely the cause of the color difference. While it also records IR
light most of the IR a galaxy emits due to dust warmed by star formation
is at wavelengths greater than Sloan can see.

While Sloan has imaged the area the data is yet to make it into NED so I
wasn't going to make an annotated image. But then I saw there were 4
other asteroids in the frame besides the obvious one. They were too
faint to point out without annotation and a few galaxies were in NED
with redshift information so I decided to make one anyway. In doing so
I found one galaxy, WIG R00J233224443-02450563, with a redshift of
z=1.110560 which puts it at over 8 billion light-years. That is the
WiggleZ Dark Energy Survey. It tends to list very high redshift
galaxies. Makes me wonder if these are quasars rather than galaxies
that I am seeing. Or is it just a very bright but normal (for one that
far back in time) galaxy I'm picking up. It is in the right side of my
image and labeled with its magnitude as well as distance using NED's 5
year WMAP calculation. For more on the WiggleZ survey see:
http://wigglez.swin.edu.au/site/ The page says it covers galaxies with
a redshift of 0.2 to 1 yet this one exceeds 1 though not by a lot. For
more on the survey including where the name comes from see:
http://www.science.org.au/nova/115/115key.html

It seems most asteroids I catch in my images are moving in retrograde
motion. These are the exception as all are moving in prograde that is
to the east (left).

Sloan image:
http://cseligman.com/text/atlas/ngc7694wide.jpg

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net